One of the DVD (Digital Versatile Disc) playback-only standards is the DVD video format. In this DVD format, content data, such as video and audio, is multiplexed with data of various subpictures such as subtitles, and is recorded as a program stream on a disc. Also navigation data for interactive playback of the stream is recorded on the disc.
Here, the interactive playback represents playback performed such that a user uses various DVD functions such as, in addition to playback from a preference position and playback in order of preference, a multi-angle function capable of playing back video captured at various angles, a multi-language function capable of playback in a language of preference among a plurality of languages, and a parental control function that prevents playback of a certain scene such as a violent scene.
In a program stream, a plurality of audio streams and a plurality of subtitle streams can also be multiplexed. This makes it possible to record subtitle data of a plurality of different languages on a single disc for, for example, a single piece of video content such as a movie, whereby the user can select audio and subtitles in a language of preference when playback of video is initiated and while video is being played back.
A system in which a user can easily download content such as effect sound, moving pictures and still images, which are used as materials of a video product, is disclosed in Patent Document 1. In addition, a technology that can replace data of a part of the entirety of music data by other data is disclosed in Patent Document 2.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-140662    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2002-311967